this quote from Carl Jung is truly great:
"The world is full of people suffering from the effects of their own unlived life. They become bitter, critical, or rigid, not because the world is cruel to them, but because they have betrayed their own inner possibilities. The artist who never makes art becomes cynical about those who do. 1/2
Cauchy Distribution ✍️
Statistics has a villain. A probability distribution that looks perfectly reasonable sits symmetrically around a center point has a bell-shaped curve and yet breaks almost every statistical tool ever invented. The Cauchy distribution has no mean. The Cauchy distribution has no variance. Averaging samples from the Cauchy distribution does not converge. The Cauchy distribution is the distribution that statisticians use to teach humility.
The Cauchy distribution looks similar to the distribution the familiar bell curve that describes heights, test scores, measurement errors and many natural phenomena. Both the Cauchy distribution and the normal distribution are symmetric. Both peak at a center point. Both taper off toward zero in both directions.. The Cauchy distribution has tails that are much heavier. The Cauchy distribution approaches zero more slowly as we move away from the center. This visual difference in the tails is not a technicality. The difference in tails is the source of the Cauchy distribution’s properties and the reason the Cauchy distribution breaks standard statistical reasoning so completely.
Full explanation given below 👇
Push-Pull Cavity Phase Conjugate Resonator ✍️
What if you could move an object using nothing but light. Not by pushing it with light pressure in one direction but by making a small difference in how light waves work with a resonating cavity that creates a force using special light effects? That is the idea this device is trying to do.
The push-pull cavity phase conjugate resonator is an idea that uses two special light waves. One a little bit shorter in wavelength and one a little bit longer. That work inside a special kind of container that holds light. This container is called a whispering gallery mode resonator. It is a sphere made of a material where light can move around the inside and stay there with very little loss. The same idea that makes travel around the walls of a place like St. Paul’s Cathedral in London is used in this optical version to keep light moving around the edges of the sphere.
Full explanation given below 👇
One second-order equation determines the straightest curves a manifold will admit:
d²xᵏ/dt² + Γᵏᵢⱼ(x) (dxⁱ/dt)(dxʲ/dt) = 0.
Riemann supplied the metric that generates those symbols in 1854; Christoffel isolated the connection coefficients fifteen years later.
The extra terms, built from the Christoffel symbols of the metric, cancel the fictitious accelerations that the coordinates themselves produce, so the left-hand side is the covariant acceleration and vanishes.
The resulting curves are the geodesics - great circles on the sphere, meridians, the world-lines of freely falling particles.
The geometric series has a simple interpretation in the complex plane. Each new term is obtained by multiplying the previous one by r. If ∣r∣<1, its magnitude decreases while its phase can rotate the term, producing the spiral shown in the graphic.
The unit circle is the boundary of convergence. Inside it, the terms approach zero and the infinite sum approaches a finite value. On or outside the unit circle, the series does not converge in general. This is why the same geometric-series idea extends naturally from real numbers to complex analysis, where magnitude controls convergence and phase controls rotation.
Every natural transformation from a representable functor is just evaluation at one element.
Yoneda (covariant): Nat(Hom_C(A, −), F) ≅ F(A).
Given Φ : Hom(A,−) → F, set u = Φ_A(id_A) ∈ F(A). Then for any f : A → X,
Φ_X(f) = (Ff)(u).
The whole functor is recovered from a single point. That is why representable functors organize schemes, types, and polymorphic programs: relationships out of A already know F.
An object is known by the arrows that leave it.
He said these numbers were useless. Then he did the math anyway - and it worked.
In 1545 Gerolamo Cardano tried to split 10 into two numbers that multiply to 40. The answer he got was 5 + √−15 and 5 − √−15.
That was not supposed to make sense. Nobody took the square root of a negative number. Cardano said the whole thing was sophistic, as subtle as it was useless.
Then he multiplied them.
25 − (−15) = 40.
It worked.
He never really believed in those numbers. He just wrote them down, checked the arithmetic, and left the door open. Imaginary numbers start there, with a man who thought they were nonsense and calculated with them anyway.
This duality can be pursued further and is related to a duality between past and future and the notions of control and knowledge. Thus we may have knowledge of the past but cannot control it; we may control the future but have no knowledge of it.
-- C. S. (1959)